The end game should have been Shelle, because it was vital to the long-term foundation of the show. Bo and Hope's son and John and Marlena's daughter together would have set the stage for the next generation of Days.

I think this quote pretty much sums it up. MM had a wonderfull chemistry with JKJ, unfortunatelly Shelle fanbase was too strong to go against and it meant to completely rewrite 7 years of established history between the three. So when Sheffer was fired and Corday had his "letīs please fanbases for a while" mood, he asked Higley to stop it.

But Shelle were married couple with a child, basically another supercouples the show has so much trouble to write for, and portrayed by two people with zero (IMO of course) chemistry together (especially compared with Phelle) so Dena really didnīt know what to do with them.